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一个TTL 反相器可以用作一个有源放大器,做成一个简单的、便宜的晶体控制振荡器,只需要小于2平方时的空间,频率容差从0°～70℃小于0.01%。一、工作原理振荡器的设计如图1所示。通过L_1和R_1的直流通路把反相器置于门槛区域内,使得U_1变成不稳定,而象一个处于截止区和饱和区之间的线性放大器。C_1、C_2、C_3、Y_1及U_1的输出阻抗组成一个晶体Π型线路,形成频率选择反馈以防止三次谐波振荡。L_1的交流阻抗须要足够高,以消除对晶体网络的任何负载影响;这样,网络的d(?)/df 特性就不会被L_11—R_1偏置线路破坏。振荡器的反相器供给增益A,晶体Π型网络供给反馈β,要求满足振荡条件Aβ≥1<0。C_4的作用是保证线路在晶体频率起振。所有其他元件的响应时间和晶体响应时间(由晶体的机械质量所决定)相比是非常快的。电源内阻和C_4的组合使电
A TTL inverter can be used as an active amplifier to make a simple, inexpensive crystal controlled oscillator that requires less than 2 square feet of space and has a frequency tolerance of less than 0.01% from 0 ° to 70 ° C. First, the working principle Oscillator design shown in Figure 1. The inverter is placed in the threshold region through the DC path of L_1 and R_1, making U_1 unstable and like a linear amplifier between the cutoff region and the saturation region. The output impedances of C_1, C_2, C_3, Y_1 and U_1 form a crystal Π-type line, forming a frequency selective feedback to prevent the third harmonic oscillation. The AC impedance of L_1 needs to be high enough to eliminate any load effects on the crystal network; in this way, the network’s d (?) / Df characteristics will not be destroyed by the L_11-R_1 bias line. Oscillator inverter supply gain A, crystal Π network supply feedback β, required to meet the oscillation conditions Aβ ≥ 1 <0. The role of C_4 is to ensure that the line starts oscillating at the crystal frequency. The response time of all other components is very fast compared to the crystal response time, which is determined by the mechanical quality of the crystal. Power supply resistance and C_4 combination of electricity